Dynamics of soil enzyme activities during critical growth stages in rice and wheat under conservation agriculture-based management practices

Conservation agriculture (CA)-based practices reduce the risk of soil nutrient depletion by promoting the stabilization and sequestration of organic carbon (C) and enhancing soil biological functioning. To address this, a field study was conducted to quantify the impact of rice establishment methods, tillage and residue management practices for eight-years to identify the critical growth stages of rice and wheat for assessing the biological properties of soil under rice-wheat cropping system (RWS). The results revealed that direct seeded rice-reduced tillage followed by zero tillage (ZT) with residue retention significantly improved soil's extracellular enzyme activities except phenol oxidase (PHEOX) and peroxidase (PERO) across five growth stages of rice-wheat systems. Dehydrogenase (DHA), fluorescein diacetate (FDA), alkaline phosphatase (Alk-P), β-glucosidase (β-glu), total polysaccharides carbon (TPC) and cellulase (CELL) activities were highest at the maximum tillering stage of rice and wheat than at other growth stages. At the maximum tillering stage of wheat, activities of DHA, FDA, Alk-P, β-glu and TPC under ZT-wheat with residue retention were 60.5, 35.8, 50.6, 30.4, and 31.1% higher than conventional tillage (CT) without residue. Furthermore, ZT-wheat with residue retention significantly increased wheat grain yield by 10.6% as compared to CT without residue. Principal component analysis (PCA) suggested that xylanase, phenol oxidase and FDA can be used as sensitive parameters for assessing soil quality under rice establishment methods, tillage and residue management practices in RWS. These findings highlight that practices like ZT with residue retention support sustainable intensification of RWS by enhancing soil biological fertility and crop productivity.